ok. To clarify... I've seen many many articles showing how you can use twitter to do X. When it just seems that there's already a far more suited way to do X.
I'm sure it's sort of useful for some things for some people, but I can't see it going mainstream.
Someone uses the telephone to do telemarketing to try to sell you carpet and from that you understand what the telephone is "for"?
IM/IRC/email/blog are all different - from each other and from Twitter. As is the telephone. Or SMS. Or...